Network equipment such as a router and a switch generally has a packet filtering function. The filtering function is a function mainly limiting the circulation or changing the destination of packets matching a condition for filtering, which is predefined in an ACL (Access Control List).
The filtering function may be implemented in software or hardware. Filtering functions implemented in software (as disclosed in JP-T-2008-505561 or JP-A-8-18599, for example) have high flexibility while disadvantageously having a low processing speed. Therefore, the implementation in hardware is more suitable for processing a large number of packets at a high speed.